ORAU Team

Dose Reconstruction Project for NIOSH

Technical Basis Document for Paducah Gaseous 

Diffusion Plant - Introduction

Document Number:

ORAUT-TKBS-0019-1 

Effective Date: 09/09/2004

Revision No.: 00

Controlled Copy No.:

Page 1 of 6 

_______

Subject Expert: Jay J. Maisler

Document Owner

Approval: Signature on File Date:

 Jay J. Maisler, TBD Team Leader 

09/08/2004

Approval: Signature on File Date: 

 Judson L. Kenoyer, Task 3 Manager

09/07/2004

Concurrence: Signature on File Date: 09/08/2004

 Richard E. Toohey, Project Director

 

Approval: Signature on File Date: 09/09/2004

Supersedes:

 James W. Neton, Associate Director for Science

 None

TABLE OF CONTENTS

Section Page

RECORD OF REVISION ..................................................................................................................... 2 

ACRONYMS AND ABBREVIATIONS.................................................................................................. 3 

1.0 PURPOSE............................................................................................................................... 4 

2.0 SCOPE.................................................................................................................................... 5 
Effective Date: 09/09/2004 Revision No. 00 Document No. ORAUT-TKBS-0019-1 Page 2 of 6

RECORD OF ISSUE/REVISIONS

ISSUE 

AUTHORIZATION

DATE

EFFECTIVE 

DATE

REV.

NO. DESCRIPTION

Draft 05/17/2004 00-A New technical basis document for the Paducah

Gaseous Diffusion Plant – Site Profile. Initiated by 

Jay J. Maisler.

Draft 06/08/2004 00-B Addressed OCAS comments. Initiated by Jay J. 

Maisler.

Draft 07/07/2004 00-C Addressed additional OCAS comments. Initiated 

by Jay J. Maisler.

09/09/2004 09/09/2004 00 First approved issue. Initiated by Jay J. Maisler.
Effective Date: 09/09/2004 Revision No. 00 Document No. ORAUT-TKBS-0019-1 Page 3 of 6

ACRONYMS AND ABBREVIATIONS

EEOICPA Energy Employees Occupational Illness Compensation Program Act of 2000

DOE Department of Energy

DOL Department of Labor

GM Geiger-Muller 

HHS Department of Health and Human Services

ICPMS Inductively Coupled Plasma Mass Spectrometry

kerma kinetic energy released per unit mass

NIOSH National Institute for Occupational Safety and Health

ORAU Oak Ridge Associated Universities

OWCP Office of Worker Compensation

PGDP Paducah Gaseous Diffusion Plant

TBD technical basis document

TLD thermoluminescent dosimeter

TRU transuranic
Effective Date: 09/09/2004 Revision No. 00 Document No. ORAUT-TKBS-0019-1 Page 4 of 6

1.0 PURPOSE

This Site Profile represents a specific support mechanism documenting historical practices at the 

Paducah Gaseous Diffusion Plant (PGDP). This Site Profile can be used to evaluate both internal 

and external dosimetry data for monitored workers and can serve as a supplement to individual 

monitoring data. For unmonitored workers, information is presented in this document that provides for 

estimations of internal and external doses. 

This document provides a site profile of PGDP that contains technical basis information to be used to 

evaluate the total occupational radiation dose that may reasonably be associated with a worker’s 

radiation exposure for claimants under the Energy Employees Occupation Illness Compensation 

Program Act (EEOICPA). This dose results from exposure to external and internal radiation sources 

in PGDP facilities, to PGDP occupationally-required diagnostic X-ray examinations, and to on-site 

environmental releases. Methods for estimating doses that may have occurred while an employee 

was not monitored, inadequately monitored, or missed due to analytical detection limits or incomplete 

or missing monitoring records (i.e., “missed dose”) are included. Over the years new and more 

reliable scientific methods and protection measures have been implemented. The methods needed to 

account for these changes are also identified in this document.

Energy employee radiation doses are evaluated using the NIOSH Interactive RadioEpidemiological 

Program and the Integrated Modules for Bioassay Analysis (IMBA) computer program. Information on 

measurement uncertainties is an integral component of the NIOSH approach. This document 

describes how to evaluate uncertainty associated with PGDP exposure and dosimetry records.

Technical Basis Documents (TBD) and Site Profile Documents are general working documents that 

provide guidance concerning the preparation of dose reconstructions at particular sites or categories 

of sites. They will be revised when additional relevant information is obtained about the affected 

site(s). These documents may be used to assist NIOSH in the completion of the individual work 

required for each dose reconstruction.

In this document the word “facility” is used as a general term for an area, building or group of buildings 

that served a specific purpose at a site. It does not necessarily connote an “atomic weapons 

employer facility” or a “Department of Energy facility” as defined in the Energy Employees 

Occupational Illness Compensation Program Act of 2000 (42 U.S.C. § 73841 (5) and (12)).

2.0 SCOPE

The Site Profile is divided into six major sections: this Introduction, Site Description, Occupational 

Medical Dose, Occupational Environmental Dose, Occupational Internal Dose, and Occupational 

External Dose. Some sections are accompanied by an attachment that provides the critical data for 

the specialists reconstructing the doses.

The Site Description TBD (ORAUT-TKBS-0019-2) is a brief description of the facilities and processes 

used in processing and enriching uranium. The purpose of the gaseous diffusion plant has been and 

continues to be the enrichment of uranium, initially for military applications and subsequently for 

commercial nuclear reactor fuel. PGDP enriches feed material in the form of uranium hexafluoride 

(UF6) gas from approximately 0.711% 235U up to about 2.5% 235U. The enriched product from PGDP 

was sent to other U. S. Department of Energy (DOE) gaseous diffusion plants at Portsmouth, Ohio, 

and Oak Ridge, Tennessee, for further enrichment. Some feed material was recycled uranium

obtained from spent reactor fuel.
Effective Date: 09/09/2004 Revision No. 00 Document No. ORAUT-TKBS-0019-1 Page 5 of 6

The Occupational Medical Dose TBD (ORAUT-TKBS-0019-3) provides information about the dose 

individual workers received from X-rays required as a condition of employment. The PGDP 

occupational medicine program required pre-employment and regular diagnostic chest X-ray 

examinations. The examinations consisted of one posterior-anterior and one lateral chest projection. 

In addition to parts of the body exposed in the primary beam of an X-ray machine, other tissues 

receive some dose from secondary radiation. Secondary radiation consists of X-rays that are 

scattered from surrounding materials or that escape from the source assembly. In this TBD, tables 

are provided that list claimant-favorable estimated dose equivalents to organs of the body that result

from single and combined posterior-anterior and lateral chest X-rays for male and female PGDP 

employees. The tables are derived from an assessment of the air kerma at the source-to-skin 

distance, based on specific operating parameters for the facility, insofar as these are known.

The Occupational Environmental Dose TBD (ORAUT-TKBS-0019-4) applies to workers who were not 

monitored for external or internal radiation exposure. The environmental dose is the dose workers 

received when working outside the buildings on the site from inhalation of radioactive materials in the 

air and direct radiation exposure from sources, such as the depleted uranium hexafluoride cylinders in 

storage. 

Inhalation of environmental radionuclides results in internal dose to the whole body or body organs. 

The internal dose for workers outside of the facilities was determined from the air concentrations 

resulting from the releases from stacks, individual building releases, and from the purge cascade and 

other operations at PGDP. Unmonitored workers may have been exposed to occupational doses 

internally from on-site releases into the air. Air concentrations of radionuclides were determined using 

annual environmental reports and are provided from 1952 through 1996. Values for airborne 

concentrations and annual intakes are provided for total uranium and 99Tc.

Site annual environmental reports, health physics surveys, and other reports were reviewed for data 

that would be useful in reconstructing ambient radiation levels. Ambient radiation dose rates includes 

natural background radiation and from sources within the facility.

PGDP personnel have annually compared these data with thermoluminescent dosimeter (TLD) data 

from offsite locations and literature values for state and regional exposure levels. The determination 

has always been that onsite ambient radiological conditions as measured at the security fence are not 

significantly different from offsite, state, and regional annual exposure levels. This is attributed to the 

geology of the region around PGDP. Exceptions to this observation have been monitoring locations 

near depleted uranium cylinder storage yards in recent years. These locations show an increase in 

external exposure as the inventory of depleted uranium increased. The approach for estimating 

external dose using this information is provided in the TBD.

The Occupational Internal Dosimetry TBD (ORAUT-TKBS-0019-5) describes the internal dosimetry 

program at PGDP. The primary method for monitoring employees for intakes of radionuclides at 

PGDP was urine bioassay, which was instituted at the start of enrichment operations and has 

continued to the present day. However, the focus of the monitoring program in the early years was 

the detection of excreted soluble uranium. When monitoring for less soluble isotopes of uranium and 

transuranic (TRU) elements was necessary, in vivo methodologies were implemented to supplement 

the excretion data. These methods were primarily whole-body counting and chest (lung) counting.

Until the mid-1980s, action levels were set based on the amount of uranium excreted. Later, intakes 

and doses were assessed based upon both in vivo and in vitro monitoring results. Data are available 

from 1952 to the present for both in vivo and in vitro analysis records and associated interpretations.
Effective Date: 09/09/2004 Revision No. 00 Document No. ORAUT-TKBS-0019-1 Page 6 of 6

A review of in-house procedures used to assess the concentration of uranium in urine indicates that a 

variety of quality control steps were an integral part of the process. Therefore, the in vitro results from 

in-house processing, typically reported in units of micrograms of uranium per liter, are considered to 

be generally reliable. However, interpretation of those results can be difficult, primarily because of 

uncertainty regarding enrichment and solubility, the contribution of environmental uranium, and 

because samples were collected at work and during the middle of the work week, meaning that crosscontamination and the inability to unfold soluble from insoluble intake fractions contribute to the 

uncertainty.

Guidance on selection of source terms is provided in the TBD. Input parameters for the interpretation 

of in vivo and in vitro measurement results are presented, including instructions for assessing dose for 

both monitored and unmonitored employees. The detection limits of the various in vivo and in vitro

methodologies and potential missed dose are discussed. Existing data analysis is summarized and 

significant incidents with internal dose potential are identified.

The Occupational External Dosimetry Program TBD (ORAUT-TKBS-0019-6) describes the program 

for measuring skin and whole body doses to the workers from sources that were external to the body. 

The methods used at the PGDP have also evolved over the years as new techniques and equipment 

have been developed. In addition, concepts in radiation protection have changed. The dose 

reconstruction, PGDP practices and policies, and dosimeter types and technology for measuring the 

dose from the different types of radiation are discussed in this section. Attention is given to the 

evaluation of doses measured from exposure to beta, gamma, and neutron radiation.

Sources of bias, workplace radiation field characteristics, responses of different beta/gamma and 

neutron dosimeters in the workplace fields, and the adjustments to the recorded dose measured by 

these dosimeters during specific years are presented in detail. In addition, the sources of potential 

dose that could be missed because of the limitations of dosimetry systems and the methods of 

reporting low doses are presented as a function of dosimeter type, year, and type of radiation.